I'm looking for Normal Whole Brain Volume Dose Tolerance for single fraction SRS Brain plans. We have historically used V(1200cGy) < 10cc but with people using single isocenters to treat multiple mets it's becoming easier to treat more mets than before. I would assume we are able to push the "limit" of the historic normal whole brain tolerance but there isn't much literature with regards to this. If you do use a larger tolerance than above, please share and include literature references if there are any. Thank you.